This invention relates to a photoconductive material for use in electrophotography and, more particularly, to a photoconductive material comprising an electroconductive support and, formed thereon, a photoconductive layer incorporated with a hydrazone compound.
In conventional electrophotography, inorganic substances such as selenium, cadmium sulfide, amorphous silicon, and zinc oxide have been widely used in the photoconductive layer of photoconductive materials. In recent years, however, numerous researches are in progress to use organic photoconductive substances in photoconductive materials.
Fundamental properties required for the photoconductive materials to be used in electrophotography include (1) high charge acceptance when exposed to corona discharge in darkness, (2) low attenuation, in darkness, of the charge produced by corona discharge, (3) rapid dissipation of the charge when exposed to light, and (4) low residual charge after the exposure to light.
Selenium and cadmium sulfide widely used in conventional photoconductive materials are photoconductors which meet the above requirements with respect to fundamental properties. They have, however, disadvantages associated with their production such as, for example, high toxicity, difficulties encountered in film formation, lack of flexibility, and high cost. In view of the future exhaustion of natural resources, the production of inorganic substances will be limited. As a consequence as well as for the reason of environmental pollution originated from the toxic inorganic photoconductors, replacement of inorganic substances by organic photoconductors is desired. Under the circumstances, photoconductive materials prepared by using various organic substances have been proposed and some of them are in actual use. General advantages of organic photoconductors over inorganic substances are better transparency, lighter weight, easier film formation, ability to acquire both positive and negative charges, and easier fabrication.
Examples of typical organic photoconductors heretofore proposed include polyvinylcarbazole and derivatives thereof. These compounds, however, are not satisfactory in film-forming properties, flexibility, solubility, or adhesiveness. Although a certain degree of improvement was achieved by sensitizing polyvinylcarbazole with a pyrylium salt dye (Japanese Patent Publication No. 25,658/73) or with 2,4,7-trinitrofluorenone (U.S. Pat. No. 3,484,237), an organic photoconductor which meets the fundamental requirements mentioned above as well as required mechanical strengths and a sufficient durability has not yet been obtained.